Flask. Free-kassa. Как пофиксить 500 internal server error?

Сейчас пишу обработчик для фри кассы на пайтоне , фреймворк фласк. Ошибка 500 и не пишет даже в консоли эту ошибку.

    @app.route('/inpay/', methods=['POST'])
def inpay():
  request.form['MERCHANT_ID'].encode('utf-8')
  request.form['MERCHANT_ORDER_ID'].encode('utf-8')
  request.form['AMOUNT'].encode('utf-8')
  sign = hashlib.md5(request.form['MERCHANT_ID']+':'+request.form['AMOUNT']+'secretkeyfromfreekassaaaa'+request.form['MERCHANT_ORDER_ID'])
  ips = ['136.243.38.147', '136.243.38.149', '136.243.38.150', '136.243.38.151', '136.243.38.189', '136.243.38.108']
  print(str(request.headers.get('X-Forwarded-For', request.remote_addr).split(", ")[0]))
  if str(request.headers.get('X-Forwarded-For', request.remote_addr).split(", ")[0]) in ips:
    con = sq.connect('db.sqlite')
    cur = con.cursor()
    cur.execute("""UPDATE users SET balance = balance + ? WHERE name == ?""", (request.form['AMOUNT'], session['nm']))
    con.commit()
    con.close()

    return 'YES'
  else:
    return 'bad ip'